Difference between three tier vs. n-tier

Question

I just came across the following sentence:

As the industry has moved from a three tier model to n-tier models, the object relational impedance mismatch has become more prevalent.

But I can't find a concise explanation of the difference between three tier and n-tier. I know what three tier is, and I assume n-tier just adds one or more tiers. I'm just not sure what these additional tiers would be. If anyone has a short explanation or simply a good link, that would be much appreciated.

Answer 1

hi pls check this link, so u can get good idea regarding this

http://msdn.microsoft.com/en-us/library/ms973829.aspx

Answer 2

Where is that quote from? What industry are they referring to? I would have to imagine that this has something to do with SOA because that is the only thing that makes sense for this kind of statement.

Most people that I have heard who make this kind of statement believe that in a service-oriented domain each service is somehow its own tier. I disagree as most of the time these disparate services can be logically grouped into the common three tiers anyhow (presentation, logic, and data). But again, its all pretty subjective.

Answer 3

Without seeing the sentence in context, I assume it is referring to the explosion in services and middleware.

Answer 4

n-tier implies n is any number - when n=3 then it is the same as n-tier.

The usual definition of 3-tier is presentation, logic & data (in any order), and yes, SOA can confuse the neophyte because sometimes it sits in the data tier, sometimes the logic tier and sometimes both logic & data tiers.

The whole subject is...subjective. If you need some tiers then call it n-tier - if you know that n=7 then call it 7-tier, or n-tier.

Answer 5

If we looked at tiers like being layers of a cake; each layer would have it's own ingredients and do it's own things. The tiers of each application interact with only the tier above it, or below it.

3-tier means the cake has 3 layers. Usually it's data at the bottom, then an application logic tier (PHP/ruby/etc), and then a presentation tier at the top (html)

Having an n-tier architecture means you design something multiple layers layer to it. The number of layers you have will depend on how you decide to make it.

It seems to make a lot more sense with larger, or web applications.

I usually end up with a 5 tier application. Each tier can only interact with the one above it or below it. This can provide fantastic extensibility and standardization across your application.

Client Tier

Web Browser

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Presentation Tier

Render the HTML - Coldfusion/Flash/Ruby/PHP,etc.

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Business Logic Tier

Run the processes and calculations as needed - Coldfusion/Flash/Ruby/PHP,etc.

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Data Integration Tier

(Queries from my Development Language, Stored Procedures, etc.)

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Data Tier

(Database - MySQL, etc)

Answer 6

This Wiki-book chapter on application architecture is a straightforward guide to layers, tiers, and deciding what you need to use.